1. Technical Field
The present invention relates to a broadcast information notification method and a network node which notify a mobile station of broadcast information by using a paging message and a broadcast message.
2. Background Art
The 3GPP has been discussing about the “ETWS (Earthquake and Tsunami Warning System)” for distributing emergency information (broadcast information) such as earthquake information and tsunami information.
Here, with reference to FIG. 7, description is given of operation for notifying a mobile station UE of emergency information (Primary Notification) in the “ETWS”.
As shown in FIG. 7, when detecting an input from a CBE (Cell Broadcast entity) in Step S3001, a CBC (Cell Broadcast Center) transmits a Write Replace message to a radio controller RNC in Step S3002.
In Step S3003, the radio controller RNC transmits a “System Information Request” set at “CTCH Indication=0”, to a radio base station BTS.
In Steps S3004 and S3005, the radio controller RNC notifies, to each mobile station UE belonging to each paging group, emergency information (Primary Notification) by using a paging message (Paging Type 1).
Thereafter, in Steps S3006 to S3008, the radio controller RNC repeatedly notifies, to the mobile station UE, detailed information (Secondary Notification) of the emergency information by using a CBS (Cell Broadcast Service) message (broadcast message).
In the above-described ETWS, the emergency information needs to be transmitted to the mobile station UE by secure communication, since a danger such as transmission of emergency information by an unauthorized radio base station BTS is conceivable.
The ETWS structure has a problem that emergency information cannot be transmitted by secure communication at the radio interface between the radio controller RNC and the mobile station UE, although being assumed to be transmitted by secure communication using a dedicated line or an IPsec at the interface between the radio controller RNC and the CBC.
Specifically, since a radio link for secure communication is not established between the radio controller RNC and the mobile station UE at the time when the emergency information is transmitted, transmission of the emergency information by secure communication is not possible at the radio interface between the radio base station BTS and the mobile station UE.
In addition, each of multiple mobile stations UE needs to judge whether or not the same paging message received by the multiple mobile stations UE is a paging message directed to the mobile station UE itself, even if a link for security communication is established between the radio controller RNC and the mobile station UE. For this reason, the network cannot provide security by using security information assigned individually to the mobile stations UE.